The invention generally relates to closed loop fluid flow circuits and, more particularly, relates to closed loop fluid flow circuits for testing diesel engines.
In the testing of engines, it is typically necessary to measure the flow of fuel to the engine, as well as monitor and maintain the temperature of the fuel to the engine. Proper measurement and temperature fluctuation minimization result in more reliable test data. More specifically, the measurements regarding the flow of fuel can be used for, among other things, ascertaining the efficiency with which the engine runs, while the temperature of the operating fuel provides useful indications as to the potential pollutants being released by the engine and therefore assuring compliance with environmental regulations.
Better compliance can be achieved both by better process control and, ultimately, by better understanding of the engine product. That is, production and development margins can be tightened simply because the inputs affecting power growth are more tightly controlled. Proof that compliance is achieved under both steady-state and transient conditions can also be conclusively documented at regulatory agency specified conditions.
Previously, there was a coupling of cycle power and fueling rates. By fixing the input conditions to the engine throughout the cycle, emission sensitivity to intentional engine design changes become more apparent instead of being masked by this coupling.
In addition, for a fixed volumetric fuel delivery, cooler engines generally operate with more efficiency and more power such that control of the fuel to and from the engine can have a sizable effect on the power with which the engine operates.
Systems have therefore been developed which both measure the flow of fuel consumed by a test engine, and condition the fuel flowing to the engine. For example, Larson, U.S. Pat. No. 4,404,847, discloses a fuel supply conditioning and flow measurement circuit for testing fuel injectors wherein a fuel supply is drawn upon and communicated through a fluid flow circuit to the fuel injectors. A flow meter is provided in line with a fluid flow circuit, and a refrigeration device is provided to cool the fuel. However, a mechanism for separating return fuel flow is not provided, nor is a mechanism for heating the fuel flow if needed.
Haynes, U.S. Pat. No. 4,450,820, also discloses an engine fuel conditioner and monitor. Haynes discloses a conditioning tank intermediate the fuel supply and the engine. Fuel is drawn from the conditioning tank by the engine, with excess fuel being recycled back to the conditioning tank. A flow meter is provided intermediate the fuel tank and the conditioning tank and a single heat exchanger is disclosed to be disposable either in the conditioning tank, or in the fuel tank. However, first and second heat exchangers separate from the conditioning tank are not disclosed, nor is a mechanism for taking into account the density of incoming fuel.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a fuel measuring and conditioning system is disclosed which comprises a consumed fuel measurement system and a fuel conditioning control loop.
In another aspect of the present invention, a fuel measuring and conditioning system is disclosed which comprises a mixing tank, a consumed fuel measurement system and a fuel conditioning control loop. The mixing tank includes an outlet adapted to supply fuel to an engine and an inlet adapted to receive fuel from the engine. The fuel measurement system includes a flow meter, while the fuel conditioning control loop includes first and second heat exchangers, and a circulation pump. The fuel measurement system includes an inlet adapted to receive a supply of fuel from a facility storage tank and an outlet in fluid communication with the fuel conditioning control loop. The fuel conditioning control loop includes an inlet connected to the mixing tank and an outlet connected to the mixing tank.
In another aspect of the present invention, a method of measuring and conditioning fuel for an engine is provided which comprises the steps of communicating fuel to the fuel conditioning control loop, measuring the flow of fuel flowing into the fuel conditioning control loop, pumping fuel from the mixing tank to the first and second heat exchangers and back to the mixing tank, measuring the temperature of the fuel within the mixing tank, recycling fuel from the mixing tank to the engine and back to the engine while measuring return fuel flow with a secondary flow meter [used for control purposes only; feed forward control], and controlling the flow of cooling/heating media to the first and second heat exchangers based on the temperature of the fuel in the mixing tank.
In accordance with another aspect the present invention, a closed loop transient diesel fuel conditioning and measurement system is provided which comprises a mixing tank, an engine supply/return loop, a fuel conditioning loop, a first heat exchanger, a second heat exchanger, a fuel inlet conduit, a flow meter, and a density meter. The mixing tank includes first and second inlets and first and second outlets. The first inlet and first outlet are adapted to be connected to a diesel engine. The fuel conditioning loop is connected to the mixing tank second inlet and second outlet. The first heat exchanger is interposed in the fuel conditioning loop and includes a heating medium. The second heat exchanger is also interposed in the fuel conditioning loop, but includes a cooling medium. The fuel inlet conduit includes an inlet and an outlet with the outlet being connected between the mixing tank second outlet and the fuel conditioning control loop and the inlet being adapted to be connected to a source of fuel. The flow meter and density meter are interposed in the fuel inlet conduit.
These and other aspects and features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.